This invention concerns wheel chocks used to secure motor vehicles on the decks of transporters, especially railway cars.
Most motor vehicles, such as automobiles, are moved between assembly and distribution sites by rail transport. Since railway cars are subjected to substantial impact loads and vibrations, it is essential that the carried vehicles be securely held in place on the decks of the cars during transit. For many years, the conventional holding scheme employed tie down chains which interconnected the vehicle body and the structure of the rail car and which were tightened to compress the suspension springs of the vehicle. Lately, however, increasing attention has been given to restraint schemes employing wheel chocks. Considerable study and research conducted by the railroad and automotive industries has revealed that four chocks, positioned fore and aft of each wheel on one side of a vehicle, afford adequate restraint under usual loading conditions, and that protection against dislodgment under abnormal loads can be provided by equipping each set of chocks with an over-the-wheel harness. The investigators have also considered the practical matter of design compatibility, for it is recognized that car interchange is an integral part of railroad life in America. As a result of this activity, it has been decided that all chocks must be adapted for releasable attachment to a prescribed mounting rail of hat shape in cross section which extends lengthwise of the car and each of whose upright walls contains a uniform pattern of locking holes. The design of the chock itself has not been, and may never be, standardized, and a variety of proposals have been made. However, at least as far as we are aware, none of the various designs has proven entirely satisfactory.